Cellular communication systems provide wireless communication services in many populated areas of the world. While cellular communication systems were initially constructed to service voice communications, they are now called upon to support data communications as well. The demand for data communication services has exploded with the acceptance and widespread use of the Internet. While data communications have historically been serviced via wired connections, cellular users now demand that their wireless units also support data communications. Many wireless subscribers now expect to “surf” the Internet, access email, and perform other data communication activities using their cellular phones, wireless personal data assistants, wirelessly linked notebook computers, and/or other wireless devices. The demand for data communications in wireless communication systems continues to increase with time. Thus, existing wireless communication systems are currently being created or modified to service these burgeoning data communication demands.
Cellular networks include a network infrastructure that wirelessly communicates with wireless terminals within a respective service area. The network infrastructure typically includes a plurality of base stations dispersed throughout the service area, each of which supports wireless communications within a respective cell or set of sectors. The base stations may be coupled to base station controllers (BSCs), with each BSC serving a plurality of base stations. Each BSC is coupled to a mobile switching center (MSC). Each BSC also typically directly or indirectly coupled to the Internet.
In operation, each base station (BS) communicates with a plurality of wireless terminals operating in its cell/sectors. A BSC coupled to the base station routes voice communications between the MSC and the serving base station. The MSC routes the voice communication to another MSC or to the PSTN, for example. The BSCs route data communications between a servicing base station and a packet data network that may include or couple to the Internet. Transmissions from base stations to wireless terminals are referred to as “forward link or downlink” transmissions while transmissions from wireless terminals to base stations are referred to as “reverse link or uplink” transmissions.
Third generation (3G) cellular networks have been specifically designed to fulfill these future demands of the mobile Internet. As these services grow in popularity and usage, factors such as cost efficient optimization of network capacity and quality of service (QoS) will become even more essential to cellular operators than it is today. These factors may be achieved with careful network planning and operation, improvements in transmission methods, and advances in receiver techniques. To this end, carriers need technologies that will allow them to increase downlink throughput and, in turn, offer advanced QoS capabilities and speeds that rival those delivered by cable modem and/or DSL service providers. In this regard, networks based on wideband CDMA (WCDMA) technology may make the delivery of data to end users a more feasible option for today's wireless carriers.
A mobile handset may synchronize its timing to the timing of a base station to enable the mobile handset to communicate via the network. In some conventional WCDMA networks, synchronization and timing acquisition between a mobile handset and a base station, or coarse acquisition, may comprise at least a 3-step process. The first step is referred to as a slot timing process. The second step may be referred to as a frame timing process. The third step may involve determining the scrambling code utilized by the base station that was identified during the slot timing and frame timing processes. A signal scrambled at a base station by utilizing a selected scrambling code may be unscrambled by utilizing the selected scrambling code at the mobile terminal. The mobile terminal may utilize a plurality of potential scrambling codes when determining which of the potential scrambling codes is utilized at the identified base station. The mobile terminal may utilize the selected scrambling code to unscramble a spread spectrum signal received from the base station.
After establishing coarse acquisition, the mobile handset may need to perform fine acquisition to adjust timing signals at the mobile handset to maintain synchronization with the base station in spite of Doppler effect frequency shifts that may occur with some mobile terminals, and other sources that may cause a loss of timing synchronization between the mobile handset and the base station. The mobile handset may perform fine acquisition by computing a frequency offset between a current received symbol and a previous received symbol. The mobile handset may receive a current symbol by accumulating a plurality of symbol segments. Similarly, the previous received symbol may comprise a plurality of symbol segments. The mobile handset may accumulate the symbol segments contained within the previous received symbol before beginning to accumulate symbol segments contained within the current received symbol. Consequently, the mobile handset may experience a one symbol delay between a time instant at which a current adjustment of timing signals may occur, and a time instant at which a subsequent adjustment of timing signals may occur.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.